OSC 9 notification produces [Invalid UTF-8] with multibyte UTF‑8 characters in msg

[dolzenko]

Issue Description

Originally when using ghostty with codex cli and conversation contains Russian chars I was getting

on task completion.

Expected Behavior

Proper notification message

Actual Behavior

Notification doesn't appear

Reproduction Steps

1. Open Ghostty
2. Run bash -c 'p=$(printf "a%.0s" {1..254}); printf "\033]9;%sЯ\007" "$p"'

Ghostty Logs

No response

Ghostty Version

Ghostty 1.3.1-arch2

Version
  - version: 1.3.1-arch2
  - channel: tip
Build Config
  - Zig version   : 0.15.2
  - build mode    : .ReleaseFast
  - app runtime   : .gtk
  - font engine   : .fontconfig_freetype
  - renderer      : renderer.generic.Renderer(renderer.OpenGL)
  - libxev        : io_uring
  - kernel version: 7.1.6-arch1-1
  - desktop env   : other
  - GTK version   :
    build         : 4.22.2
    runtime       : 4.22.4
  - libadwaita    : enabled
    build         : 1.9.0
    runtime       : 1.9.3
  - libX11        : enabled
  - libwayland    : enabled

OS Version Information

arch

(Linux only) Display Server

Wayland

(Linux only) Desktop Environment/Window Manager

No response

Minimal Ghostty Configuration

# No configuration required.

Additional Relevant Configuration

No response

AI Usage Disclosure

I used OpenAI Codex to help investigate the root cause, implement and test a candidate fix, and edit this report. I reviewed the report and code changes.

I acknowledge that:

• I have reviewed the FAQ and confirm that my issue is NOT among them.
• I have searched the Ghostty documentation and confirm there doesn't exist a configuration option that solves my issue.
• I have searched the Ghostty repository (both open and closed Discussions and Issues) and confirm this is not a duplicate of an existing issue or discussion.
• I have checked the "Preview" tab on all text fields to ensure that everything looks right, and have wrapped all configuration and code in code blocks with a group of three backticks (```) on separate lines.

[jcollie]

#13795